1. Field of the Invention
The present invention relates to a cartridge magazine for explosive powder charge-operated setting tools including a charge-receiving member having a plurality of spaced from each other, charge-receiving chambers for receiving propellant charges, respectively, and a bottom for closing the charge-receiving chambers.
2. Description of the Prior Art
German Publication DE-OS 23 24 183 discloses a cartridge magazine having a charge-receiving member with a plurality of spaced from each other, propellant charge-receiving chambers. Each of the chambers is covered by a thin bottom. A propellant charge is located inside each of the chambers. A heating wire, which is connected with a source of electrical current and which ignites the propellant charge upon being heated, is embedded into the propellant charge.
A proper insertion of the heating wire into the propellant charge-receiving chamber cannot be effected economically. Further, the formation of an electrical connection between the current source and the heating wire is associated with substantial difficulties.
Accordingly, an object of the present invention is to provide a cartridge magazine that can be economically produced.
Another object of the present invention is to provide a cartridge magazine in which the propellant charges can be electrically ignited in a simple manner, with simple means, and reliably.
These and other objects of the present invention, which will become apparent hereinafter, are achieved, according to the present invention, by forming the bottom, which covers the propellant charge-receiving chambers, of a heat-releasing, fusible and current-conducting foil.
The formation of the bottom according to the present invention provides for localized melting of the foil and a reliable ignition of the propellant charge with droplets of the hot melt.
A reliable localized heating with subsequent melting is achieved when the bottom is formed of a foil having a thickness, preferably, from 0.1 mm to 0.5 mm.
In order to insure that in the cartridge magazine the separate chambers of which contain a small amount of a propellant charge, a sufficient amount of the propellant charge is provided in the region of the bottom, preferably, the side of the bottom adjacent to the chambers is provided with a glue layer. Particles of the propellant charge adhere to this glue layer, e.g., when the cartridge magazine is subjected, during transportation, to vibrations that cause swirling inside the propellant charge-receiving chamber.
Improved ignition of the propellant charge is preferably achieved when an ignition-supporting, initiating charge is provided in the propellant charge-receiving chamber in its bottom region.
In order to be able to use, e.g., a powdery initiating charge and to prevent its mixing with the propellant charge, e.g., upon occurrence of vibrations, a separation layer, which separates the initiating charge from the propellant charge, extends, preferably, at least in the region of the propellant charge-receiving chamber, between the bottom and the propellant charge-receiving member.
For manufacturing reasons, advantageously, the separation layer has a thickness from 0.02 mm to 0.5 mm.
A particularly good localized heating and melting of the bottom is achieved when, preferably, the bottom is formed of aluminum.
In order to be able to achieve a localized melting of the foil, the foil cooperates with two electrical contacts of a source of an electrical current of which one contact is formed as an electrode, which is received in and is guided by an insulator connectable with the bottom. The second contact is connected with the bottom itself. Thus, the electrical current flows through both the electrode and the bottom. The insulator keeps the electrode spaced form the bottom in order to insure that an electric arc can be formed between the electrode and the bottom upon flow of the electrical current therethrough. A large amount of heat is released in the electric arc region which is sufficient for melting the foil in the electrode region.
The foil can be so dimensioned that its resistance becomes a dominating resistance of the electrical circuit. In this way, the electric energy, which is provided by the electrical current source, is primarily used for melting the foil.
Upon melting of the foil, a portion of the melt is evaporated. The expandable gas generates a steam pressure which displaces droplets of the melt towards the powdery propellant charge causing its ignition.
An increase of the available electrical energy is achieved by combustion of gases which are formed during melting of the foil. The necessary oxygen becomes available due to formation at the free end of the insulator an expansion chamber, which is open at the free end and into which preferably the electrode extends.
In order to be able to increase the flow velocity of the expandable gas leaving the expansion chamber, advantageously, the inner width of the expansion chamber diminishes toward the free end of the insulator.
In order to be able to additionally heat the gas formed during the evaporation of the foil, care should be taken to insure that it flows from the insulator toward the foil and is carried through the electric arc. This provides for additional heating of the gas which increases the flow velocity and the speed of movement of melt droplets toward the propellant charge. In order to insure that the expandable gases are carried only through the electrical arc, the smallest inner width of the expansion chamber is so selected that it corresponds to the cross-section of the electrode which extends parallel to the inner dimension of the expansion chamber.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings.